The present invention relates generally to axial flow rotary separators for threshing and separating grain crops and the like, of a type typically embodied in a combine and more particularly to the threshing and separating sections of rotors for such machines.
As is well known and typical of such separators, a rotor rotates in a stationary housing which includes grate portions and an upstream inlet for receiving harvested crop material. Threshing and separating of grain take place as the crop material is conveyed, through interaction between rotor and housing, spirally downstream through the separator in the annular space between the rotor and the housing. Threshed grain and chaff is expelled through the grate or grates and straw is discharged from the downstream end of the separator.
Typically, rotors carry generally axially extending threshing and separating bars while the inside surfaces of the housing and grates are provided with members to effect an axial indexing or conveying of the material, such as raised helical ribs, either continuous or interrupted. However, in axial flow separators relying upon such fixed and passive lead members, it has been found that material flow is often uneven and inconsistent so that threshing and separating efficiency are adversely affected and it is known to modify threshing and separating bars so that they also have an axial indexing effect in an attempt to improve material conveying and control. For example, the individual ribs of a threshing rasp bar may be appropriately angled or the threshing and separating bars themselves may be disposed helically rather than axially on the rotor. However, in attempting to combine the functions of threshing or separating and conveying in one rotor member, the efficiency of one or both functions must be compromised because the physical characteristics of rotor elements required for each function differ. For example, it is known that on a threshing rotor, threshing bars with ribs or blades fine enough to produce the best threshing results are only marginally effective as conveyors, even if the blades are suitably angled. And in the separating portion, axially extending bars are most efficient in separating but of course have no direct conveying effect.